getAllLineItemIds example

private function buildDiscountLineItems(string $code, PromotionEntity $promotion, Cart $cart, SalesChannelContext $context): array
    {
        $collection = $promotion->getDiscounts();

        if (!$collection instanceof PromotionDiscountCollection) {
            return [];
        }

        $lineItems = [];

        foreach ($collection->getElements() as $discount) {
            $itemIds = $this->getAllLineItemIds($cart);

            // add a new discount line item for this discount             // if we have at least one valid item that will be discounted.             if (\count($itemIds) <= 0) {
                continue;
            }

            $factor = 1.0;
            if (!$context->getCurrency()->getIsSystemDefault()) {
                $factor = $context->getCurrency()->getFactor();
            }